NEW YORK (AP) – A grand jury is nearing the end of its probe of the police killing of an unarmed black man last year in a fusillade of 50 bullets, with a decision possible on criminal charges as early as mid-March, lawyers and union officials involved in the case said Tuesday.

Beginning this week, a parade of star witnesses will answer questions before grand jurors who must decide whether any of the five shooters should be indicted in the death of Sean Bell – an episode that sparked community outrage and raised questions about police tactics.

Two companions of Bell who were seriously wounded in the shooting are expected to testify Friday, the lawyers said. Next week, the officers themselves could appear as the final witnesses and give their side of the undercover operation gone awry.

The lawyers predicted the grand jury, which began hearing evidence in January, could vote on whether to indict in mid-or late March. The plodding pace of the investigation has not been surprising given the complexity of the case and the fact that jurors have been meeting only three days in week, they said.

“We’re getting close to the end,” said Charlie King, who represents three other friends of Bell who were scheduled to go before the panel on Wednesday to offer eyewitness testimony. He said his clients will say the officers opened fire without warning.

At least three of the four detectives under investigation – Gescard Isnora, Marc Cooper and Paul Headley – plan to appear individually in the closed-door proceedings, union officials said.

Those three “are anxious to give their side of the story to the grand jury,” said Mike Palladino, president of the Detectives’ Endowment Association. “In my opinion, the jurors can’t make an informed decision without it.”

It reamins unclear whether Detective Michael Oliver – whose 31 rounds far exceeded any other officer – will volunteer his sworn testimony, which risks locking any witness into one version of events that could be used as evidence at trial. His attorney, James Culleton, said no decision has been made about whether his client will testify.

The fifth shooter, Officer Michael Carey, “is still keeping his options open,” said his lawyer, Stephen Worth.

Officials with the Queens District Attorney’s office declined comment.

Bell, 23, was killed the before dawn on Nov. 25 after his bachelor party at Kalua Cabaret, a topless bar in Queens where police had launched an undercover operation in response to complaints about prostitution. Union representatives and lawyers for the officers have said their clients became convinced Bell and his friends were going to retrieve a gun from a car parked around the corner after overhearing them get into an argument with another patron.

When Mr. Isnora, an undercover detective, approached the car – driven by Bell and carrying the two other men – it lurched forward and bumped him, then twice rammed into an unmarked police minivan, police said.

Mr. Isnora, who has claimed through his lawyer that he spotted one of the men make a suspicious move, squeezed off 11 rounds before the vehicle came to a stop. Of the other plainclothes detectives, Mr. Oliver fired 31 bullets, Mr. Cooper shot four times, and Mr. Headley fired once. Mr. Carey shot three times.

The three victims were black; the officers are both black and white. All have been taken off undercover duty and put on paid leave.

One major point of contention: Mr. Isnora’s attorney has said that before his client opened fire, he pulled out a badge and identified himself as an officer. But the survivors, Trent Benefield and Joseph Guzman, say that never happened, said their attorney, Sanford Rubenstein.

On Friday, the pair “intend to full cooperate with the grand jury and simply tell the truth about what happened,” Mr. Rubenstein said.